Pneumatic tool lubricant

ABSTRACT

A lubricant for reducing or eliminating airborne lubricant exhaust mist in ambient air when used by a tool driven by compressed air. The lubricant includes between about 58 vol % and about 90 vol % polyalphaolefin or polyalphaolefin blend, and between about 10 vol % and about 42 vol % complex ester compatible with the polyalphaolefin or polyalphaolefin blend. The ester includes polymeric molecules with a cohesive tendency to adhere to each other, and when subjected to shear stresses, to form elongate filaments.

This application is a divisional application of U.S. patent applicationSer. No. 12/998,783, which was the national stage entry under 35 U.S.C.§371 of International Patent Application No. PCT/CA2009/001724, filed onJun. 1, 2011, which claims priority from U.S. Provisional PatentApplication No. 61/193,443, filed Dec. 1, 2008, all of which areincorporated by reference herein. All claims of priority to theaforesaid applications are hereby made.

BACKGROUND OF THE INVENTION

(i) Field of the Invention

The present invention relates to a lubricant for an air line oiler orlubricator for use with various types of pneumatic tools and motors, andmore particularly, relates to an improved lubricant for use withpneumatic rock drills and the like.

(ii) Description of the Related Art

Air line lubricators are well known for supplying compressed air with alubricant or oil so that pneumatic tools and motors can be continuouslylubricated to minimize wear during use. Pneumatic rock drills, forexample, are particularly prone to wear due to their use in environmentshaving significant amounts of water and other contaminants present inthe compressed air supply, as well as due to the high load and torqueconditions imposed on the tool in certain rock formations and inbolting. It is therefore important to maintain an effective oil film oninternal tool surfaces.

U.S. Pat. No. 3,040,835 issued Jun. 26, 1962 discloses a typical airline lubricator for supplying compressed air with a lubricant or oil forlubricating pneumatic rock drills.

Surgical tools often are driven by compressed air to avoid electricalsparks in the combustible environment of an operating room due to thepresence of oxygen and anesthetics. The pneumatic motors of the surgicaltools are lubricated by an oiler that feeds a predetermined quantity ofa lubricant into the compressed air driving the pneumatic motors. Aquantity of lubricating oil is exhausted from the pneumatic tool intothe operating room and it is desirable to use an effective lubricantwhich is non-toxic and does not produce an exhaust mist in an operatingroom environment.

U.S. Pat. No. 5,427,203 issued Jun. 27, 1995 discloses an air linelubricator system for introducing a lubricant to compressed air whichdrives a pneumatic motor of a surgical tool used in an operating roomand for recovering and recycling lubricant to minimize discharge oflubricant into the operating room.

Petroleum greases also are known for lubrication of pneumatic toolsbecause of their higher initial viscosity than petroleum oils and theirattribute of better adherence to metal surfaces. However, there is somequestion as to the overall effectiveness of grease as opposed to oilsunder certain conditions, especially cold ambient temperatures as wellas in overhead drilling and bolting conditions. Although they have ahigher initial viscosity than petroleum based rock drill oils, andtherefore may help to reduce fogging, greases have a viscosity index ofonly 94 typically, which means that they thin out somewhat more rapidlyunder high temperature operating conditions, than do conventionalpetroleum rock drill oils. Therefore, their high viscosity in thelubricator restricts the amount of grease entering the air supply, whichis desirable for reducing oil fog, but their tendency to lose viscosityunder high heat conditions could result in the tool being starved ofenough lubricant under certain conditions to meet the lubricationrequirements of the tool, potentially resulting in premature wear. Thiswould be predictable if the grease is exposed to high temperatureoperating conditions within the tool, causing the grease to loseviscosity and to be exhausted more rapidly by the high velocity airpassing through the tool than replenishment by the cooler, thickergrease within the lubricator. In other words, the grease is exiting thetool faster than it is entering it. As well as the aforementionedproblems, when the tool lubed with grease is stopped, and cools down,the grease becomes so thick that it clogs the air chambers and the drillwon't restart, or starts in a sluggish manner.

It is a principal object of the present invention to provide alubricating oil for pneumatic tools which provides improved lubricationwith very little oil fog generation.

Petroleum based rock drill oils produce significant amounts of oil mistin the exhaust air, which tends to coat the tool, drill rods and thedrill operator with oil, making the equipment slippery and obstructingthe operator's vision and breathing.

It is another object to provide a cost-effective lubricating oil whichis non- toxic in environments with very limited ventilation, such asunderground mining areas and in operating rooms, and which produces aminimum of oil mist.

SUMMARY OF THE INVENTION

These and other objects of the invention will become apparent from thefollowing description.

We have found surprisingly that low to high viscosity polyalphaolefins(PAO) having viscosity in the range of 2 to 3000 centistokes (cSt),preferably 2 to 10 cSt, and most preferably 9 or 10 cSt, (grade rated at100° C.) such as are sold under the trademark SpectraSyn™, or Synfluid™,along with a PAO compatible polymerized shear stable, complex ester suchas is sold under the trademarks SYN-ESTER® GY-56 by Lubrizol Corporationor PRIOLUBE™ sold by Croda Lubricants, with the addition of ananti-wear/extreme pressure, corrosion and rust and oxidation packagesuch as KX 1236M (KX1255) sold by King Industries, have been found toprovide unexpectedly improved lubrication and wear performance forpneumatic tools and air motors over a wide range of operatingtemperatures and with low emission of airborne mist.

More particularly, the blend of polyalphaolefin, along with apolymerized ester of the invention, as well as an anti-wear, extremepressure (EP), corrosion and rust and oxidation (R/O) package, used as alubricating oil for pneumatic tools and air motors, provides uniqueadvantages, as follows:

-   -   improved lubrication with extended service life of the air tools        and motors.    -   Dramatic reduction in the generation of oil mists or “fog”. Oil        mist contamination is at or below American Conference of        Governmental Industrial Hygienists (ACGIH) recommended new        threshold limit value (TLV) standard of 0.2 ppm.    -   Dramatic reduction in the quantity of oil required to        effectively lubricate tools—between ⅓ and ½ of the quantity        typically required based on a petroleum based lubricant.    -   Improved environmental appeal as the lubricant is inherently        biodegradable and is used in greatly reduced quantities    -   Improved protection against water contamination due to the        polarity of the tenacious film provided by the lubricant, which        provides an unbroken barrier between the water and the tool.    -   Improved worker health and safety, as the lubricant is composed        of ingredients that are generally recognized as safe.

In its broad aspect, the invention provides a lubricant for reducing oreliminating airborne lubricant exhaust mist in ambient air when used bya tool driven by compressed air. The lubricant includes between about 58vol % and about 90 vol % polyalphaolefin or polyalphaolefin blend, andbetween about 10 vol % and about 42 vol % complex ester compatible withthe polyalphaolefin or polyalphaolefin blend. The ester includespolymeric molecules with a cohesive tendency to adhere to each other,and when subjected to shear stresses, to form elongate filaments.

In another of its aspects, the lubricant additionally includes about 1.5to 2 vol% of an anti-wear/extreme pressure, corrosion, and rust andoxidation additive.

In yet another aspect, the lubricant has a viscosity in the range of 75to 300 cSt at 40° C.

In another of its aspects, the complex ester has a polar molecularstructure imparting to the lubricant a negative charge, wherein thelubricant is attracted to metal surfaces inside the air tool made ofpositively charged ferrous metal and forms a tenacious film on the metalsurfaces.

In yet another aspect, the lubricant comprises about 73.3 vol % of thepolyalphaolefin or polyalphaolefin blend, about 25 vol % of the ester,and about 1.7 vol % of the anti-wear/extreme pressure, corrosion andrust and oxidation additive.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Typical mechanisms for introduction of a predetermined quantity of alubricating oil into compressed air by the use of air line lubricatorsis disclosed in aforementioned U.S. Pat. Nos. 3,040,835 and 5,427,203.Conventional lubricating oils are hydrocarbon products from petroleumoils which are discharged by carry-over with exhaust air from the toolinto the ambient air system. This tends to cause fogging in the generalvicinity of the tool exhaust, which in turn causes discomfort andpotential respiratory concerns to operators in the vicinity. A typicalhydrocarbon oil lubricant used for lubricating pneumatic rock drills,for example, is sold by Petro Canada in Canada under the name ARDEE150™.

Although the description will proceed with reference to pneumatic rockdrills, namely jacklegs and stoppers, it will be understood that themethod of the invention has utility with pneumatic equipment such aslong hole drills, jumbos, jack hammers, breakers, chipping hammers andbolters and with industrial tools such as drills, orbital sanders,ratchets, hammers, bolters, chisels, socket drives, cutters and thelike, and with surgical tools and with air motors, and air cylinders.

Although it is understood that we are not bound by hypotheticalconsiderations, it is believed the PAOs are specially designed chemicalsthat are uniquely made from alpha olefins. These stable molecules areproduced by:

-   -   Steam cracking hydrocarbons to produce ultra high-purity        ethylene    -   Ethylene oligomerization to develop 1-decene and 1-dodecene    -   Decene or dodecene oligomerization to form a mixture of dimers,        trimers, tetramers and higher oligomers

The PAO's used in the invention are hydrogenerated olefin oligomersmanufactured by the catalytic polymerization of linear alphaolefinshaving viscosities of about 2 to about 3000 centistokes (cSt),preferably about 2 to 10 cSt, and more preferably 9 to 10 cSt,identified as for example SpectraSyn™ 9 or 10, or Synfluid™ 8 or 9. ThePAOs are used in combination with esters derived from various alcoholsand of various viscosities which may be achieved through polymerizationand/or hydrogenation having the characteristics of SYN-ESTER® GY-56manufactured by Lubrizol Corporation, or PRIOLUBE™, manufactured byCroda Uniqema. Coupling agents may be used to ensure the long termstability of the lubricant.

Although low viscosity PAOs in the range of 2 to 10 cSt are preferred,the combination of a low viscosity PAO such as 10 cSt with higherviscosity PAOs such as PAO 100 cSt or higher are operative as a blend.However, the blends of low and higher viscosity PAOs have been found tonegatively impact the stability of the lubricant, when blended with thelow molecular weight ester, compared to the stability of the formulamade with a single low viscosity PAOs of 10 cSt and less. PAO 10 is thepreferred low viscosity polyalphaolefin because, in addition to itsstability, it is used at a higher ratio in the formulation than theother low viscosity PAOs, resulting in the most economical and stableformulation.

The addition of anti-wear, extreme pressure, corrosion, rust andoxidation inhibitors, such as produced by King Industries of Norwalk,Conn. and sold under the product name KX 1236M, also named KX1255, in anamount of about 1.5 to 2 vol % of the total lubricant composition, hasbeen found to aid anti-wear, extreme pressure and anti-wear, corrosionand rust and oxidation performance of the lubricant composition.

Table 1 following shows formulations for Exxon Mobil PAO products andfor Chevron Phillips PAO products to achieve various product viscositiesas referred to by “PT” designations at 40° C. It will be understood thatPAO designations used herein are grade rated at 100° C. but thatfinished oils designated PT are rated at the standard commercialtemperature of 40° C. Accordingly, by way of example, PAO 10 having aviscosity of 10 cSt at 100° C. would have a viscosity of 66 cSt at 40°C.

TABLE 1 PT 75 89% PAO 9 Chevron OR 85% PAO 8 EXXON or Chevron 9.3% GY-5613.3% GY-56 1.7% KX 1236M King Industries 1.7% KX 1236M PT 100 85% PAO10 EXXON OR 80% PAO 9 Chevron 23.3% GY-56 18.3% GY-56 1.7% KX 1236M 1.7%KX 1236M PT 125 79% PAO 10 Exxon OR 74% PAO 9 Chevron 19.3% GY-56 24.3%GY-56 1.7% KX 1236M 1.7% KX 1236M PT 150 73.3% PAO 10 Exxon OR 68% PAO 9Chevron 25% GY-56 30.3% GY-56 1.7% KX 1236M 1.7% KX 1236M PT 175 69% PAO10 Exxon OR 65% PAO 9 Chevron 29.3% GY-56 33.3% GY-56 1.7% KX 1236M 1.7%KX 1236M PT 200 66.6% PAO 10 Exxon OR 61.3% PAO 9 Chevron 31.7% GY-5637% GY-56 1.7% KX 1236M KX 1236M PT 220 63% PAO 10 Exxon OR 59% PAO 9Chevron 35.3% GY-56 39.3% GY-56 1.7% KX 1236M 1.7% KX 1236M PT 270 58%PAO 10 Exxon OR 55.9% PAO 9 Chevron 40.3% GY-56 42.4% GY-56 1.7% KX1236M (KX1255) 1.7% KX1236M (KX1255)

Conventional petroleum based lubricating oils have a threshold limitvalue, for airborne particulate, determined as a guideline by theAmerican Conference of Governmental Industrial Hygenists (ACGIH) forrecommended safe levels of hazardous materials in the workplace, of 5.0parts per million (ppm). However, for 2009 the ACGIH has recommendedthat the threshold limit value for oil mists be reduced to 0.2 ppm. Ithas been found that, due to the use of reduced injection rates and dueto the tenacious cohesiveness of the lubricant compositions of thepresent invention, air quality measurements have been recorded at orless than 0.2 ppm in the workplace.

Applicants have found that the addition of 0.6 litre of applicants'lubricant to rock drills consuming about 4750 litres per minute (175cfm) for an eight-hour shift provided 0.262 ppm lubricant oil in thecompressed feed air for the eight hours for a high viscosity PT 270 oil.A lower viscosity PT 75 oil consumed 0.6 litre of the oil for afour-hour shift providing 0.524 ppm of lubricant oil in the compressedair feed for four hours. Almost none of the oil at the lower about 0.2ppm or at the higher about 0.55 ppm became airborne.

Petroleum based rock drill oils and greases are not biodegradable andmust be remediated or recovered if spilled or aspirated onto the ground.The present composition is completely biodegradable and does not poseany threat to aggregate surfaces upon which it is aspirated.

Lubricants made from vegetable oils are well known. Tests conducted onoils derived from castor oil and canola oil indicated good lubricationbut the oils have a number of issues that make them unsuitable for rockdrill oils. For example, vegetable oils have poor low temperatureproperties, in that they thicken excessively, and can even become solidat temperatures encountered when compressed air is decompressed, orduring cold weather operation. Vegetable oils are oxidatively unstable,and when they are exposed to air they tend to form varnishes that canharden to the point of seizing the tool. They are also hydrolyticallyunstable, and can form sticky, gooey deposits when combined and agitatedwith condensation often found in compressed air. Castor oil is a knownirritant, and although it is useful in closed systems, it can causeworker discomfort when aspirated into the work environment.

The lubricant base stocks of the present invention having viscositiesranging from about 7 to 3000 cSt at 40° C., preferably 2 to 100 cSt, andmore preferably about 9 or 10 cSt, are competitive in cost/use comparedto petroleum based materials, resist fogging, when combined with theappropriate ester, are stable at elevated temperatures, have very littleodor and have excellent oxidative stability. The syntheticpolyalphaolefin (PAO) of the invention is produced by, but not limitedto, Exxon Mobil Corporation and sold under the trade-mark SpectraSyn™,or by Chevron Corporation and sold under the trade-mark Synfluid™. Thepolyalphaolefin is fortified with a low molecular weight, complex, i.e.polymerized ester, preferably, but not limited to Lubrizol GYS56™,manufactured by Lubrizol. Polymerized esters manufactured by CrodaUniqema, and other manufacturers, can also be used, but may be limitedbased on their compatibility with PAO's, as well as their shearstability. Lubrizol GY-56™ in combination with PAO-10, for example, in aratio of PAO to low molecular weight complex ester in the range of about1.5:1 to about 20:1, preferably in a ratio of about 1.5:1 to 9:1, hasbeen found to provide excellent lubricating protection. Tests conductedby the manufacturers have shown the PAOs and the esters to be non toxic.

Petroleum based oils are non polar in nature. Lubricant manufacturersmust rely on additives to ensure that the oils adhere to metal surfaces.However, metal to metal motion creates a “squeegee” effect which tendsto displace petroleum oil. Oil flow must be adequate to ensure that theoil film is constantly replenished. The absence of a consistentpetroleum oil film could eventually result in tool failure. Petroleumrock drill oils sometimes are formulated with an emulsifier and, aswater from the compressed air lines enters the lubricant, theemulsifiers are designed to mix the oil with the water to maintain awater-in-oil emulsion so as to avoid oil washout by the water, in whichcase the tool would not be protected. However, when there is a lot ofcondensation present in the air lines, the emulsifier tends to dilutethe oil to a lower viscosity, resulting in less viscous lubricating filmthat is less effective than in its original form and the lubricant maybecome too thin to protect the tool. The tool life as a result maydiminish, unless the operator compensates by increasing oil flow to thetool, which typically results in fogging. Additionally, some mine watersare corrosive, emphasizing the need for a tenacious lubricating filmbetween the air/water and the tool surfaces.

The composition of the present invention, on the other hand, contains apolar molecular structure in the form of hydroxyl (-OH) molecules whichimpart to the fluid a negative charge. Ferrous metals are positivelycharged elements and the net result is that the composition is attractedto ferrous metals, forming a uniform lubricating film across the entiresurface of the metal with which it comes in contact. This film isextremely tenacious, i.e. very difficult to displace, and is verydurable. Therefore, as long as minute amounts of the lubricant pass overthe metal surface, even without the constancy demanded by petroleumbased products, proper lubrication will be assured. In one test, thelubricator containing applicants' lubricant was intentionally shut downcompletely. After 10+ minutes of operation, the tool began to warm upand eventually began to stall. The tool was allowed to cool, thelubricator was reopened allowing applicants' lubricant to flow throughthe lines, and the tool began to function normally, without any apparentdamage.

Attempting this with petroleum based product could result in a damagedtool that might need to be rebuilt.

Several tests of the lubricant of the invention were conducted, asfollows:

Initial Bench Testing:

A new Boart Longyear S-250™ jackleg was fitted with a Boart Longyearfootball style lubricator, which was then connected to an IngersollRand™ 185 compressor. The compressor was operated at 185 cfm @ 110 psi.The manufacturer's specifications dictate an operating condition of 175cfm @ 90 psi, so the drill was inadvertently operated at a “red line”conditions. The lubricator was filled with a 200 grade of applicant'slubricant, and the drill was mounted on a base without the drill rodsteel installed. Also, there was no water supplied to the tool. Thispractice is not recommended, as the drill body absorbs all of the heatand impact energy that would normally be transferred into the drillsteel rod. As a result the drill operates at a very high temperature,and the energy from the hammer piston is transferred to internal drillcomponents, typically causing drill damage or total failure. The actualtemperature of the drill housing was measured at 93° C., which was toohot to handle. Under actual operating conditions, when an air operatedhammer type of tool becomes very hot, it can cause a “dieseling” effectwith the compression chamber, in which case the lubricant actuallyignites or oxidizes, losing its lubricating properties. This typicallyresults in a shortened service life or damage to the tool. Also,freewheeling experienced during this type of test (excess RPM—no load)can cause unusual wear.

The drill was operated for two hours under these conditions, and wasrepeatedly started and stopped during the test, to determine if thedrill would seize up. The drill restarted without fail, and without aloss of RPM's due to heat induced shrinking of clearance tolerances.

Upon completion of the bench test, the drill was disassembled, andinspected by a Boart Longyear technician, commonly referred to as a“drill doctor”. The expected result was damage to the tool. However, thedrill doctor reported no unusual wear symptoms or unacceptablediscoloration of the metal surfaces due to excessive internal heatbuild-up.

Site Test #1—Liberty Mine, Timmins, Ontario

The first field test of applicants' lubricant was undertaken at LibertyMine near Timmins, Ontario, Canada on a pair of pneumatic rock drills,i.e. a jackleg and a stopper. The drills were used to create a ventraise to surface, involving overhead drilling and blasting of asiliceous rock ceiling. When the ceiling has been blasted down andmucked out (cleared), the miners come back into the area, scale theblasted surface, and stand on the blasted rock to drill the next set ofrounds. There was virtually no ventilation, providing worst possibleoperating conditions in which to test. Using only 35 to 40% of theamount of PT 150 rock drill fluid of the present invention compared toPetro Canada's ARDEE 150™ rock drill oil consumption, the operatordrilled successfully and without any fog. He also reported being muchcleaner than was typical when drilling with conventional petroleum basedrock drill oil.

When operating with petroleum oil based rock drill oil, the drill wouldfrequently experience operating problems due to water in the compressedair freezing upon exit of the drill's compression chamber. The operatorhad to stop the tool and chip the ice away from the exhaust port. Thisdid not happen after switching to the appropriate grade of applicants'lubricant.

The petroleum oil also made the operators' faces, safety glasses andoilers coated with an oily film by shift's end. After switching toapplicants' lubricant PT 150, the operators were oil free.

The conventional petroleum oils made the drill and steel drill rodsslippery, and it was often necessary to stop work to rub gloves withrock drill fines to get a grip. There were no slippery deposits on thetool using applicants' lubricant, primarily because the amount of oilthat was being injected had been reduced to the point wherein oilydeposits on the tools had been virtually eliminated, and also due to thefact that the applicant's lubricant did not create a fog which tends tosettle on the tool and objects around it, making them slippery.

While using ARDEE 150™, large amounts of water in the compressed airwould cause the water to freeze up upon exiting the muffler. In order tokeep the drill running, the driller was forced to break off the ice withhis wrench, or increase the quantity of oil injected, which caused theice to be flushed away. However, this also resulted in fogging, toolbleeding and discomfort to the drill operator.

Using the applicant's 100 cSt grade oil, the oil remained at asufficiently low viscosity to flow freely, and ice particles wereconstantly sloughed off in the compressed air stream. There was no lossof productivity due to tool freeze up.

Trial #2—Goldcorp Hoyle Pond, Timmins, Ontario

The customer previously was using Exxon/Esso Arox EP 150™ rock drilloil. Average product consumption was 10 litres per shift (average 2shifts per day). The mine operation is a narrow vein gold mine, and theequipment on which the test was conducted was a Boart Longyear BCI 2™longhole drill, on level 1020A. The heading was approximately 8′ square.Ventilation was completely shut down to prevent blowback upon theoperator.

The applicants' PT 150 lubricant was added to the tool, and thelubricator setting was not adjusted, in order to ensure that theapplicants' lubricant was allowed to completely coat all workingsurfaces of the tool. After the completion of the shift, the operatorreported that the tool was running smoothly and that there was little tono fog generated. The next morning the lubricator was adjustedconsiderably downwards, i.e. the quantity of lubricant injected wasreduced, and the tool continued working. The operator immediatelynoticed that there was virtually no fog being generated and there was noodor from the lubricant. He also mentioned that the rods were muchdrier, and that they were subsequently much easier to handle, asslippage was eliminated. Lubricant consumption was estimated to be ½ ofthe amount typically used when drilling with Exxon Arox EP 150™.Subsequently, the lubricator was further adjusted downward to about ⅓ ofits normal setting with good results.

Trial #3—Iamgold Mouska Mine—Rouyn, Quebec

Mouska Mine was a participant in the CanMet Narrow Vein Mining project,and had previously tried, unsuccessfully, to address fogging issues. Theapplicants' trial was conducted on level 13 of Mouska Mine. Productbeing used before was Esso Arox EP 150. When applicants arrived at themine site, the drilling rig, equipped with 3 Joy AL 67 drills, wasemitting enough oil fog to make it difficult to see beyond 4 or 5 feetwithin the drift. There was limited ventilation in the drift, and theoil mist was hanging in the air for approximately 8 minutes. The Joy rigoperates on approximately 600 cfm compressed air @ 90 psi. Lubricantconsumption was typically 4.5 litres of conventional petroleum rockdrill oil per shift. The lubricator was a Boart™ 9 litre capacity model.At the beginning of applicants' lubricant test, most of the Arox EP150™lubricant was emptied from the lubricator, while about 2 litresremained. The applicants' lubricant, PT 175, was added to thelubricator, and without adjustments, the drill rig was restarted. Within25 minutes (the time that it takes to clear the lines) the drill rig wasproducing considerably less fog. Within one hour, the air in the driftwas almost completely clear, in spite of the fact that there was a mixof PT 175 and Arox EP150 ™.

In order to determine the effectiveness of the low molecular weightcomplex ester in the lubricant composition, a series of tests wereconducted at another site with compressed air at 95 psig and 175 CFMwith an ambient temperature of 124° F. from the compressor using aS-250™ Boart Longyear stoper. The stoper S-250 was secured to a woodenpallet, and operated without cooling water or a steel drilling rod. Allthe heat generated by the uncooled operation of the stoper was retainedwithin the tool, which resulted in an abnormal heat build-up. Tests wererun for seven hours without wear damage to the stoper, other than minorwear to the ratchet pawls, which suffered from irregular ratcheting dueto operating without a load. All other components of the tool werewithin new tool specs.

A blend of PAO 10 (about 66 vol %), PAO 100 (about 22 vol %), GY-56(about 10 vol %), and KX 1236M (KX1255) additive (about 1.7 vol %)having a viscosity of 197 cSt at 40° C. was supplied to the S-250 stoperdrill for the seven hour test, and resulted in no visible fog. The toolran smoothly and at a relatively low temperature (134° F.), with minimallubricant leaking from the tool and very little odour.

A comparative test under the same conditions with the PAO 10 and PAO 100blend and KX 1236 M additive, but with no GY-56 ester, resulted ingeneration of fog, as well as heat buildup in the tool, eventualbleeding of lubricant from the tool and gradual choking of tool due toheat build-up and loss of clearance of the tool parts.

A PAO 10/100 blend as described above with 5 vol % GY-56, 10 vol %Cargill Agri-Pure™ 458 ester and 1.7 vol % KX 1236M (KX1255) additive,was tested under comparable conditions, and resulted in slight fog,thinning and loss of viscosity of the lubricant, and excessive lubricantbleeding and heat build-up within the tool. It is believed the presenceof the Cargill Agri-Pure 458 ester was detrimental to the lubricantblend by weakening the polymeric bonds in the GY-56 ester, causing it tobreak down and lose its viscosity with the consequence of the generationof fog.

Trial #4—JS Redpath, North Bay, Ontario

A test was conducted at JS Redpath Raise Bore Facility in North Bay,Ontario using an S-250 stoper operating with compressed air at 98 psigand 39.4° F. with Petro Canada Ardee™ 100 rock drill oil lubricant. Thetemperature of the S-250 stoper rose to 192° F. during the 25 minutetest. Some fog was noted during the tool operation with bleeding andspraying of lubricant around the tool area. A strong petroleum odour wasemitted from the tool.

The S-250 stoper was then tested with applicants' PT 120 lubricant underthe same operating conditions with no visible fog for the entire 25minute test. The maximum stoper temperature was 129° F., implying thatthe lubricating film from the applicant's PT120 was reducing frictionwithin the tool. No spraying of the lubricant, or odour from thelubricant was observed.

Trail #5—Campbell Mine, Red Lake, Ontario

A comparative test was conducted at Goldcorp Campbell Mine in Red Lake,Ontario on air motors in jackleg and stopper drills used in the drivingof raises involving difficult vertical overhead drilling. The testlasted seven months and compared the use of applicants' PT 150 lubricantwith prior art Esso AROX EP 150. Applicants' lubricant was used in 525feet of vertical timbered raise versus 750 feet of vertical untimberedraise using the prior art product. The one drill using applicants'lubricant consumed one-third the quantity of the prior art lubricant fora comparable drill with no down time due to lubricant failure. The eightjackleg and stopper drills using the prior art lubricant suffered motorseizure and scorched pistons, notwithstanding the lubricators supplyingthe oil were continually adjusted, and required down time forrebuilding. The drill using applicants' lubricant generated fog at ascale of 2 (in a scale range of 1 to 10 with 1 being best and 10 worst)whereas the drills using the prior art lubricant was rated at a scale of8. As a result, the drill using applicants' lubricant was relatively dryand easy to handle whereas the drills using the prior art lubricant wereoily and slippery and more difficult and less safe to handle.

The American Conference of Governmental Industrial Hygenists has, in thepast, recommended a TLV of 5 parts per million (ppm) for rock drilloils. New proposed changes to TLV levels by the ACGIH, based on their2005 conference, are now recommending a reduction in airborne oil miststo 0.2 ppm. Actual field tests of applicants' lubricant have proven thatthe goal of a reduction of airborne oil mists to 0.2 ppm is achievable.

Petroleum based rock drill oil and grease are not biodegradable and mustbe remediated or recovered if spilled. Applicants' lubricant iscompletely biodegradable and does not pose any environmental threats tosurface cover upon which it is aspirated.

Oxidative stability is gauged by the iodine value of an oil. The higherthe iodine value, the greater the tendency of the oil to oxidize orpolymerize to form gummy and varnish like deposits that can hamper ofeven stall the operation of an air operated tool. The ester of choice inthe formulation of applicants' lubricant has a low iodine value (<2) andhas demonstrated a very low tendency to form varnishes.

Viscosity index is a petroleum industry term. It is a lubricating oilquality indicator, an arbitrary measure for the change of kinematicviscosity with temperature. The viscosity of liquids decreases astemperature increases. The viscosity of a lubricant is closely relatedto its ability to reduce friction. Generally, it is desirable to havethe thinnest liquid/oil which maintains an unbroken lubricating filmbetween the moving surfaces, preventing metal to metal contact. If thelubricant is too thick, it will require a lot of energy to activate thetool, due to increased drag resistance. Conversely, if the lubricant'sviscosity is too low, the surfaces will contact each other, and thismetal to metal contact will cause subsequent damage. The lower theviscosity index the more dramatically the oil's viscosity will drop astemperature increases. The higher the viscosity index, the lessdramatically an oil's viscosity changes with temperature increase.

As stated above, the Viscosity Index highlights how a lubricant'sviscosity changes with variations in temperature. Many lubricantapplications require the lubricant to perform across a wide range ofconditions: lubricants must reduce not produce too much drag betweentool components when they are started from cold, and must provideadequate separation between metal surfaces when tool is running hotunder high load and torque conditions (>100 ° C.). The best oils (withthe highest viscosity index) will not vary excessively in viscosity overa broad temperature range and therefore will perform well throughout theentire temperature spectrum typically encountered in underground miningoperations.

The viscosity index of the 150 cSt lubricant of the present invention,and of the prior art tested at 100° C. are as follows, the applicants'Pneuma-Tool 150 having the highest viscosity index (VI):

-   -   Pneuma-Tool PT 150-VI 150    -   Esso Arox EP™ 150-VI 102    -   Petro Canada Ardee™ 150-VI 92

The more temperature decreases, the more dramatically the viscosity of alow viscosity index rock drill oil will increase. This is extremelyimportant when dealing with an air tool, since as compressed air exitsthe tool, it decompresses and loses latent heat from the air. That meansthat the air entering the tool is always warmer than the air exiting thetool. The net result of this loss of latent heat is a tendency formoisture in the compressed air to freeze as it exits the tool,especially when high concentrations of moisture are present in thecompressed air. Freezing of air as it exits the tool can cause an icebuild-up that can make the tool perform sluggishly, or even stall. Oncethis happens, the operator must stop work and clear the frozen ice bychipping it away with a tool. At worst, the operator must wait until thetool thaws on its own before recommencing work. If a lubricant becomestoo viscous as temperature drops, it can restrict air flow throughoutexhaust ports, and this restriction provides ideal conditions forairborne moisture to freeze in the tool. The Applicants' lubricant has arelatively high viscosity index, and tends to maintain a fluid liquidstate even under very cold conditions. It is also been demonstrated thatit is important to select a lower lubricant viscosity as conditionsbecome colder. The field test conducted at Liberty Mines showed that,even though ice was forming in the air tool due to cold temperatures anda high concentration of moisture in the compressed air, the ice wasperpetually sloughed out of the tool, along the slippery fluid surfaceof the applicants' lubricant. In other words, although ice formed, thelubricant remained at a sufficiently low viscosity to ensure that itflowed and moved the ice out of the tool.

The Four Ball Wear Test determines a lubricant's anti-wear propertiesunder boundary lubrication (metal to metal contact). Three steel ballsare clamped together to form a cradle upon which a fourth ball rotateson a vertical axis. The balls are immersed in the oil sample at aspecified speed, temperature and load. At the end of a specified testtime, the average diameter of the wear scars on the three lower balls ismeasured.

Pneuma-Tool was compared against Petro Canada Ardee 150™ and Esso AroxEP 150™

Wear test were conducted under the following conditions:

1800RPM/40° C./20 Kg. Load.

Wear Scar Results:

Esso Arox EP 150™0.31 mm

Petro Canada Ardee 150™-0.42 mm*

-   -   *Based on Petro Canada's techdata Publication IM-7817E (09.08)

Pneuma-Tool™ PT 150-0.28 mm

A more severe test was conducted based on the following conditions:

1800 RPM/75° C./40 Kg. load

Only two lubricants were subjected to this test, and as the viscositiesare not the same a direct comparison cannot be made, but inferences canbe drawn based on the wide performance spread.

Esso Arox Ep 150™ wear scar-0.60 mm

Pneuma-Tool PT 175 wear scar-0.30 mm

Table 2 below shows a summary of comparisons between applicants'Pneuma-Tool 150 and various rock drill oils and greases, with fogging,tool life, odor, consumption, washout and operational costs rated on arelative basis, with designation “1” being the best and designation “4”the worst.

TABLE 2 Esso/Exxon VULTREX Pneuma- ARDEE 150™ Arox EP EP000™ ProductTool™ Rock Drill Oil 150 ™ Grease V. Index 150 92 100 94 Fogging 1 3 3 2Wear Scar 1 4 2 3 Odor 1 3 4 2 Consumption 1 4 3 2 Washout 1 3 4 2 Oper.Costs* 1 3 4 2 *Includes operational gains from enhanced visibility,reduced slip hazards, reduced handling logistics, and otherenvironmental considerations.

The present invention provides a number of important advantages comparedto conventional rock tool lubricating oils.

A significant Reduction in the generation of oil mists or fog has beenattained. This reduction is based upon two factors of (1) the polarattraction of the lubricant to metal surfaces and (2) the cohesivetendency of the polymeric molecules to adhere to each other and to formlong, stringy filaments rather than to break apart under air pressureand velocity. A reduction in the quantity of lubricant required toprovide an effective lubricating film is due to (a) the presence ofhydroxyl groups in the oil that adhere tightly and uniformly to themetal surface and are not easily removed by mechanical action and (b)the shear stability of the lubricant that is provided by the selectionof low molecular weight shear stable polymerized basestocks that havebeen found to provide a uniform, thick film over metal surfaces that donot deteriorate under load, shear and heat. Improved workersatisfaction, health and safety is provided due to (a) the benign nature(low order of health impact) of the fluids comprising the invention, (b)the low odor of the fluids and (c) the minute amount of lubricant mistthat is generated during operation, resulting in airborne mistconcentrations at or below 0.2 ppm., which has a positive impact onrespiratory health, and which improves the hygiene conditions forworkers, based on reduced slip hazards.

Economy of use is provided, in spite of the high raw material costs ofthe fluid components, due to (a) the fact that the tenacious lubricatingfilm is not easily displaced and stays in place, (b) the structure ofthe base fluid molecules resists compressive forces (c) the fluidresists atomization and is attracted in a polar fashion to metal, it isable to perform its function as a lubricant instead of suffering lossdue to extraction by the compressed air, and (d) the lubricant is highlyoxidatively stable and resists breakdown in the presence of heat andpressure more than three times longer than conventional rock drill oils.The net result of this is a reduced consumption rate between ⅓ and ½ ofthe typical amount of petroleum oil that does the job it was intendedfor. An additional benefit is an reduced environmental impact, due tothe fact that (a) the fluid is inherently biodegradable and (b) less oilis required to do the same job as petroleum oils, so potentialcontamination is reduced.

It will be understood that other embodiments and examples of theinvention will be readily apparent to a person skilled in the art, thescope and purview of the invention being defined in the appended claims.

We claim:
 1. A lubricant for reducing or eliminating airborne lubricantexhaust mist in ambient air when used by a tool driven by compressedair, the lubricant comprising: between about 58 vol % and about 90 vol %polyalphaolefin or polyalphaolefin blend; and between about 10 vol % andabout 42 vol % complex ester compatible with the polyalphaolefin orpolyalphaolefin blend, the ester comprising polymeric molecules with acohesive tendency to adhere to each other, and when subjected to shearstresses, to form elongate filaments.
 2. A lubricant as claimed in claim1 in which the lubricant additionally comprises about 1.5 to 2 vol % ofan anti-wear/extreme pressure, corrosion, and rust and oxidationadditive.
 3. A lubricant as claimed in claim 1 in which the lubricanthas a viscosity in the range of 75 to 300 cSt at 40° C.
 4. A lubricantaccording to claim 1 in which the complex ester has a polar molecularstructure imparting to the lubricant a negative charge, wherein thelubricant is attracted to metal surfaces inside the tool made ofpositively charged ferrous metal and forms a tenacious film on the metalsurfaces.
 5. A lubricant according to claim 2 in which the lubricantcomprises about 73.3 vol % of the polyalphaolefin or polyalphaolefinblend, about 25 vol % of the ester, and about 1.7 vol % of theanti-wear/extreme pressure, corrosion and rust and oxidation additive.6. A lubricant according to claim 2 in which the polyalphaolefin orpolyalphaolefin blend has a viscosity between about 7 cSt and 3,000 cStat 40° C.
 7. A lubricant according to claim 2 in which the viscosity ofthe polyalphaolefin or polyalphaolefin blend is between 2 cSt and 100cSt at 40° C.
 8. A lubricant according to claim 7 in which the viscosityof the polyalphaolefin or polyalphaolefin blend is between about 9 cStand 10 cSt at 40° C.